In the sound motion picture camera for use with a cartridge type sound magazine there are provided a film motor for driving film and the like and a capstan motor for continuously driving the film at a constant speed past a sound recording station in combination with a drive control circuit for actuation, release and rotation of these motors. The film motor drives mechanisms for film winding up, rotation of a shutter disc and intermittent advancement of the film frame-by-frame, while the capstan motor is used to continuously rotate a capstan, pinch roller and the like by which a sound track on the film is passed at a constant speed in contact with a sound recording head in the sound recording position of the magazine. These motors are actuated and released by manipulation of a common switch almost simultaneously.
In making sound-accompanied picture taking exposure sequences with a sound magazine loaded in the camera, as the position of an aperture for taking pictures is different from the position of the sound head for sound recordings by a separation of a certain number of frames, and the film must be advanced intermittently in the picture taking station but continuously in the sound recording station, there is need to provide a certain amount of slack loop of the film between these stations.
In the conventional motor control device for the sound motion picture camera, the amount of slack loop of the film between the aperture position for taking motion picture and the sound recording head contact position was adjusted by On-Off control of the motor driving.
However, as the field of application and the performance of the motion picture camera are increased, the motor control device is required to have functions such as of selectively controlling the frame speed while still maintaining unchanged the amount of slack loop of the film necessary when the frame speed is changed, and of operating the camera with either one of the sound cartridge and silent cartridge.